Weatherproof insulated electric wire



June 30, 1942. R. w. sHoEMAKER WEATHERPROOF INSULATED ELECTRIC WIREFiled July 24,4 1940 Y w /I/ wwe/2240# Patented June 30, 1942WEATHERPROOF INSULATED ELECTRIC WIRE Richard W. Shoemaker, Woodbury,Conn., assignor to Chase Brass & Copper Co. Incorporated, Waterbury,Conn., a' corporation Application July 24, 1940, Serial No. 347,178

2 Claims.

The present invention relates to improvements in electric wires and moreparticularly to weatherproof insulated electric wires designed andadapted for use in exposed locations where the wire is subjected toweather.

One of the objects of the present invention is to provide a weatherproofinsulated electric wire having superior resistance to the destructiveeffects of moisture, sun, ice, etc.

Another object of the present invention is to provide a superiorweatherproof insulated electric wire having minimum weight for a givenelectroconductive capacity.

A further object of the present invention is to provide an electric wireof the character referred to, combining superior resistance to thedestructive effects of weather with minimum cross-sectional area for agiven electro-conductive capacity of its metallic core and maximumdielectric strength for its insulating covering.

With the above and other objects in view, as will appear to thoseskilled in the art from the present disclosure, this invention includesall features in the said disclosure which are novel over the prior artand which are not claimed in any separate application.

In the accompanying drawing, in which certain modes of carrying out thepresent invention are shown for illustrative purposes:

Fig. 1 is a broken view partly in elevation and partly in longitudinalsection of one form of Weatherproof insulated electric wire embodyingthe present invention;

Fig. 2 is a transverse sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a broken view of the same Ygeneral character as Fig. 1, butshowing another form of Weatherproof insulated electric Wire embodyingthe present invention; and

Fig. 4 is a transverse sectional view taken on the line 4-4 of Fig. 3.

The structure of Figs. 1 and 2 The so-called two wire service cableillustrated in Figs. 1 and 2 includes a central mainwire or conductor Iformed of copper or other suitable electro-conductive metal andconstituting in normal expected service what may be characterized as thehot leg of a circuit. The central main-wire III has extruded orotherwise suitably applied to it a. continuous coating of insulation IIformed predominantly of ethyl cellulose, as will be more fullyhereinafter described. Surto, is a reinforcing braid l2 formed of cottonor other suitable textile material.

Surrounding the braid I2 is an annular series of conducting-strands I3formed of copper or other suitable electro-conductive metal and jointlyconstituting what is commonly referred to as a cold leg of an electriccircuit in which the structure may be employed. The conducting strandsI3 extend generally longitudinally of the structure but on arelatively-slight helix, as is clearly indicated in the drawing, and itis preferred that the combined cross-sectional areas of the entire groupof conducting-strands I3 be equal.to the cross-sectional area of thecentral main-wire I0 when both the latter and the said group ofconducting-strands are all formed of the same material. Otherrelationships of relative conductivity may exist as betweenconducting-strands I3 on the one hand and the main wire I0 on the otherhand.

Over the group of conducting strands I3 is applied an outer braidedcover I4 formed of cotton or other suitable textile material. Over theouter braided cover I4 just referred to, and impregnated thereinto, isan outer weather-prooiing and insulating coating I5 indicated bystippling in the drawing. The weatherproof-lng coating permeates intothe material of the outer braided cover I4 as well as into theinterstices between the threads thereof and also into the spaces betweenthe group of conducting strands I3 and under some circumstances into theinner braided cover I2.

The extruded insulation I I is preferably entirely or substantiallyentirely of ethyl cellulose, and in any event the said insulation shouldbe dominantly of ethyl cellulose. By way of example the following havebeen found satisfactory and possess superior attributes both as toweather resistance and dielectric strength:

A. 90% ethyl cellulose and 10% nujol (plasticizer) plus solvent 2B. 90%ethyl cellulose, 9% dibutyl phthalate and l% Japan wax; plus solvent C.88% ethyl cellulose and 12% asphaltum; plus solvent.

The insulation II which may be conveniently applied by extrusion or, ifdesired, by wrapping a tape of the material around the central mainwireI0, is effective in a relatively-thin layer as an insulating medium andwithstands to a remarkable degree and over long periods of time thedeleterious eilects of oxygen and ozone. Furrounding the tubularinsulation II Just referred thermore, the insulation II when composeddominantly of ethyl cellulose has no observable chemical reaction withthe metal of the central mainwire I0, so that it becomes unnecessary totin the said central main-wire I to guard against disintegration ofeither the insulation or the said wire itself by chemical action.Furthermore, it has been found that an insulation such as II may berelatively thin without depriving it of full effectiveness so that theoverall dimensions of the weatherproof insulated wire may be greatlyreduced. This latter characteristic not only results in economy instorage space and materials, but also minimizes weight and the effectsof ice in weighting down the wire in service.

The outer coating I5 is preferably formed of a mixture of ethylcellulose and asphaltum or coal tar of which the following mixtures maybe mentioned by way of example:

methacrylate resin; plus solvent.

The inclusion of ethyl cellulose in asphaltum or coal tar increases theflexibility of the weatherproong coating I5 at even extremely lowtemperatures to thus avoid one of the maior defects in asphaltum or coaltar insulated compounds which are apt to crack and disintegrate underthe combined action of wind and low temperatures. Furthermore, theinclusion of ethyl cellulose with the asphaltum or coal tar effectivelyguards the tendency of the same to drip or runin extremely hot weatherand increases the over-all insulating properties of the mixture.

It is to be also noted that by employing an inner insulation such as IIdominantly of ethyl cellulose, it is possible to employ a low-cost outercoating dominantly of asphaltum or coal tarI without harmful interactionand with, a high degree of mutual adhesion.

The structure of Figs. 3 and 4 In Figs.v 3 and 4 is shown a lso-calledthree wire service cable embodying the present invention. The saidIcable is of the so-called three wire type and comprises two main-wiresI6 and I'I arranged side by side and each designed and adapted toconstitute a so-called hot leg of a circuit. Each of the main-wires I6and I1 is provided with a tubular coating of insulation I8,

which may be characterized as an inner insulation inasmuch as it iswithin an outer insulation to be later described. The said innerinsulations Iii-I8 are composed of compounds which are entirely ordominantly of Aethyl] cellulose such, for instance, as the compoundsdescribed in connection with the inner insulation II of the structure ofFigs. 1 and 2. v

Each ofthe tubular insulations IS-I is preferably surrounded by an innerbraided cover I9, each of which may be treated or impregnated with aninsulating compound such as has been described in connection with thecoating I5, prior to or after the application of the remaining featuresof the structure.

Arranged around the exterior of the two inner braided covers I9--I9 isan annular series of conducting-strands 20 formed of copper or othersuitable conducting material and having a joint conductivity preferablyequal to the joint conductivity of the main-wires I6 and I1. though 75of the service cable on a slight helix so as to permit the ready reelingo f the structure without injury.

Extending over the conducting-strands 20 and enclosing the same, as wellas enclosing the elements I6, Il, |8--I8 and I9--I9, is an outer braidedcover 2| formed of cotton or other suitable textile material.

The outer braided cover is preferably both coated and impregnated with asuitable insulating and Waterproofing coating 22 (represented bystippling in the drawing), which is preferably applied hot so as topenetrate into the material of the outer braided cover 2| as well asinto the interstices between the threads thereof and between theinterstices between the 'conductingstrands 2U. .If the inner braidedcovers IS--IQ have not been .previously treated with an insulatingcompound, it is preferable to force the material of the weather`proofing coating 22 into the structure as far as and into the saidbraided covers I S-IQ.

The material used for the weatherproong coating 22 may be of anysuitable material such as asphaltum or coal tar but preferably, andwithgreat advantage, a compound of ethyl cellulose and asphaltum isemployed, with the asphaltum or its equivalent, in this instance,dominating over the ethyl cellulose content, as hasbeen pointed out inconnection with the coating I5 of the structure of Figs. l and 2.

'I'he invention may be carried out in other specific ways than thoseherein set forth without departing from the spirit and essentialcharacteristics of the invention, and the present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the'appended claims are intended to be embraced therein.

I claim:

l. An outdoor weatherproof insulated electric wire for use in exposedlocations where the Wire is subjected -to weather and including incombination: ametallic wire; a seamless insulating coating extruded intosurrounding relation with the said metallic wire and having a majorportion of said extruded coating of ethyl cellulose and a minor portionof asphaltum; a covering of textile material surrounding the saidseamless insulating coating; and a weatherproong coating surrounding thesaid covering of textile material and containing a major portion ofasphaltum and a minor portion of ethyl cellulose.

2. An outdoor weatherproof insulated electric wire for use in exposedlocations where the wire is subjected to weather and including incombination: a metallic wire; a seamless inner insulating coatingextruded into surrounding relation with the said metallic wire andhaving a major portion of said extruded coating of ethyl cellulose and aminor portion of asphaltum; an inner covering of textile materialsurrounding the said extruded coating; a plurality of conducting strandssurrounding the said inner covering; an outer covering of textilematerial surrounding the said plurality of conducting strands; and anouter weatherprooiing coating

